The calculated distance (air line) between Khlong Luang and Prachin Buri is approximately 48 miles respectively 78 kilometers.
By car or train, the actual journey to Prachin Buri is certainly longer, as only the direct route (as the crow flies) between Khlong Luang and Prachin Buri has been calculated here.
Air line (approximately)
78 kilometers
42 nautical miles